Drainage system for internal combustion engine having a horizontally disposed crankshaft

ABSTRACT

A two-cycle internal combustion engine, which has two cylinders, has a horizontally disposed crankshaft with the crankcase divided into first and second chambers communicating with each of the cylinders and a third chamber communicating with the carburetor and with each of the first and second chambers through reed valves. Drainage, which comprises oil with some gasoline, is collected in the lowermost portion of each of the first and second chambers and directed past a check valve into a passage for supply to the other cylinder when reduced pressure exists therein. The drainage, which accummulates in the third chamber, is supplied to one of the two connecting passages through a check valve for supply to the cylinder connected to that passage.

United States Patent 1191 Sullivan et al.

[111 3,800,753 1451 Apr. 2, 1974 [75] Inventors: Patrick H. Sullivan, Milwaukee;

George W. Leidgen, Oakfield; James C. Hubbell, Fond du Lac, all of Wis.

[73] Assignee: Brunswick Corporation, Skokie, Ill.

[22] Filed: Sept. 29, 1972 [21] Appl. No.: 293,435

[52] US. Cl. 123/73 A, 123/73 PP, l23/DIG. 2,

Goggi 123/DIG. 2

3,395,679 8/1968 Christner 123/73 A Primary Examiner-Laurence M. Goodridgc Attorney, Agent, or Firm-Roy T. Montgomery; William G. Lawler, Jr.

[57] ABSTRACT A two-cycle internal combustion engine, which has two cylinders, has a horizontally disposed crankshaft with the crankcase divided into first and second chambers communicating with each of the cylinders and a third chamber communicating with the carburetor and with each of the first and second chambers through reed valves. Drainage, which comprises oil with some gasoline, is collected in the lowermost portion of each of the first and second chambers and directed past a check valve into a passage for supply to the other cylinder when reduced pressure exists therein. The drainage, which accummulates in the third chamber, is supplied to one of the two connecting passages through a check valve for supply to the cylinder connected to that passage.

4 Claims, 4 Drawing Figures DRAINAGE SYSTEM FOR INTERNAL COMBUSTION ENGINE HAVING A HORIZONTALLY DISPOSED CRANKSHAFI In a two-cycle internal combustion engine, the crankcase is part of the fuel supply system. As a result, there is no oil pan in the crankcase as in a four-cycle engine; thus, the fuel mixture must include both gasoline and oil along with air so that the oil may lubricate the bearings of the crankshaft.

In an engine having its crankshaft horizontally disposed, drainage, which includes oil with some gasoline, tends to collect in each of the chambers of the crankcase during engine idle. This includes not only the chambers communicating with the cylinders but also the chamber communicating with the carburetor and from which the mixture of gasoline, oil, and air flows into each of the chambers past reed valves.

The collection of the drainage in each of the chambers is due to the droplets of gasoline and oil condensing on the crankcase wall especially during idle.

When the speed of the engine increases, the puddle of drainage in each of the crankcase chambers communicating with a cylinder is sucked into the combustion chamber during the first few cycles. This oil rich mixture in the combustion chambers produces a smoky exhaust until the drainage in each of the crankcase chambers has been sucked into the connecting combustion chamber and burned therein.

The drainage, which has collected in the crankcase chamber communicating with the carburetor, would be removed at a slower rate because it could not flow from the carburetor communicating crankcase chamber until its level exceeded that in which it could flow through the openings, which are controlled by the reed valves, in the wall of the reed block. Thus, the smoky exhaust would continue for more than a few cycles.

One means of avoiding the creation of a puddle of drainage in the chambers of a crankcase has been to continuously drain the crankcase externally. However, this is impractical whenever the engine is employed other than as an outboard motor such as for propelling a snowmobile, for example.

The present invention satisfactorily solves the foregoing problem by providing a drainage system for a twocycle engine having a horizontally disposed crankshaft so that the drainage, which would tend to collect during idle, does not have to be drained exteriorly of the engine and without the creation of a puddle in any of the chambers of the crankcase during engine idle. The present invention utilizes a system in which oil from each of the crankcase chambers is collected at a low point and directed to the cylinder receiving a mixture of oil, gasoline, and air from the other of the crankcase chambers. The present invention further connects the crankcase chamber, which communicates with the carburetor, to one of the cylinders of the engine so that the drainage flows thereto.

By removing the drainage from the lowermost portion of the crankcase chambers during each cycle of operation, there is no opportunity for the drainage to collect in any significant amount so as to produce a puddle. Thus, this eliminates any possibility of a smoky exhaust when the engine speed is increased.

The present invention utilizes check valves to control when the drainage is removed from each of the crankcase chambers in accordance with the pressure in the cylinder to which the drainage is to be supplied. Thus, each of the check valves allows flow only when the cylinder has a reduced pressure therein.

When operating an engine in a cold climate, it is necessary to prime the engine when starting, for example. This insures that there is a fuel rich mixture in each of the cylinders during starting.

The present invention enables a fuel priming system to be incorporated with the drainage system so that the gasoline and oil mixture can be supplied directly to the cylinder without passing through the carburetor. Thus, no extra passage arrangement is necessary.

An object of this invention is to provide a drainage system for a two-cycle internal combustion engine having a horizontally disposed crankshaft.

Another object of this invention is to provide a twocycle internal combustion engine having a drainage system in which primer fuel can be selectively injected for supply to the cylinders.

A further object of this invention is to provide a twocycle internal combustion engine in which primer fuel can be introduced into the cylinders without passing through the carburetor.

Other objects of this invention will be readilyperceived from the following description, claims, and drawings.

This invention relates to a two-cycle internal combustion engine including a crankcase, a horizontally disposed crankshaft, two cylinders, and a piston disposed in each of the cylinders and connected to the crankshaft. The crankcase is divided into first, second, and third chambers by suitable means with the first chamber communicating with one of the cylinders, the second chamber communicating with the other of the cylinders, and the third chamber communicating with a carburetor or the like. Means allows each of the first and second chambers to receive a mixture of gasoline, oil, and air from the third chamber during the cycle of operation. The first chamber is connected with the one cylinder by first means to allow flow of the mixture of the gasoline, oil, and air from the first chamber to the one cylinder, and the second chamber is connected by second means with the other cylinder to allow flow of the mixture of gasoline, oil, and air from the second chamber to the other cylinder. Third means directs drainage collected in the first chamber to the other cylinder while fourth means directs drainage collected in the second chamber to the one cylinder. Drainage collected in the third chamber is directed to one of the two cylinders by fifth means.

The attached drawings illustrate a preferred embodiment of the invention, in which:

FIG. 1 is a horizontal sectional view, partly in plan, of an internal combustion engine using the drainage system of the present invention;

FIG. 2 is a perspective view of the crankcase and schematically shows the drainage system and the arrangement for supplying primer fuel to the cylinders of the engine;

FIG. 3 is a sectional view of one of the cylinders of the internal combustion engine using the drainage system of the present invention without the piston; and

FIG. 4 is a sectional view of the engine block of the internal combustion engine using the drainage system of the present invention and showing both cylinders without the pistons therein.

Referring to the drawings and particularly FIG. 1, there is shown a two-cycle internal combustion engine 10, which is particularly useful as a propulsion unit for a snowmobile. The engine includes a crankcase 11,

which has a horizontally disposed crankshaft l2 supported therein, and a cylinder block 13 conntected to the crankcase 11.

The engine 10 has a pair of cylinders 14 and 15, which have pistons 16 and 17, respectively, slidably disposed therein. Each of the pistons 16 and 17 is connected to cranks l8 and 19 of the crankshaft 12 by connecting rods 20 and 21, respectively.

The crankcase 12 is divided by a reed block 22 into a first compression chamber 23, a second compression chamber 24, and a third or reed block chamber 25. The first chamber 23 communicates with the cylinder 14 through transfer passages or ducts 26 (see FIG. 4) to transfer ports 27 of the cylinder 14 so that a mixture of gasoline, oil, and air can be supplied to the cylinder 14. Similarly, the second chamber 24 supplied a mixture of gasoline, oil, and air to the cylinder 15 through transfer passages 28 and transfer ports 29.

The third chamber communicates with a carburetor 30 (see FIG. 1) through an opening 31 in the crankcase 11. Thus, the mixture of gasoline, oil, and air is supplied initially to the third chamber 25 from which it flows to each of the first chamber 23 and the second chamber 24.

The reed block 22 has end portions 32 and 33 integrally connected to each other by a bearing support portion 34. The crankshaft 12 is supported by the bearing support portion 34 and extends through openings in the end portions 32 and 33 of the reed block 22.

Each of the end portions 32 and 33 has a plurality of openings 37 arranged in an arc. Each of the openings 37 of each of the end portions 32 and 33 is controlled by a separate reed valve 38.

Accordingly, the mixture of gasoline, oil, and air flows from the third chamber 25 to the first chamber 23 only when a reduced pressure exists within the first chamber 23 so that the pressure in the third chamber 25 can move the reed valves 38 to allow communication through the openings 37 from the third chamber 25 to the first chamber 23. A similar arrangement exists between the second chamber 24 and the third chamber 25 with the reed valves 38 allowing flow 180 of rotation of the crankshaft 12 after flow has occurred from the third chamber 25 to the first chamber 23. During the other half of the 360 of rotation of the crankshaft 12, the reed valves 38 on one of the end portions 32 and 33 close the openings 37 because of the pressure in the first chamber 23 or the second chamber 24 being greater than that in the third chamber 25 due to the piston 16 or 17 advancing into the first crankcase chamber 23 or the second crankcase chamber 24.

With the engine mounted such that the pistons reciprocate horizontally, the first crankcase chamber 23 has a lowermost area or pocket (shown at 39 in FIG. 2 for the crankcase 11) in the bottom portions of both the crankcase 1 1 and the cylinder block 13 in which drainage collects at engine idle. Likewise, the second crankcase chamber 24 has a lowermost area or pocket (shown at 40 in FIG. 2 for the crankcase 1 1) in the bottom portions of both the crankcase 11 and the cylinder block 13 in which drainage collects during engine idle.

The lowermost area or pocket 39 in the first crankcase chamber 23 communicates with a passage 41, which is formed in the crankcase 11. As shown in FIG. 2, the passage 41 extends along a sealing surface 43 of the crankcase 11, then along a surface 44 of the crankcase 11 against which the end portion 33 of the reed block 22 bears, and then along another sealing surface 45 of the crankcase 11.

The end of the passage4l communicates (schematically shown in FIG. 2) with a passage 46 (see FIG. 3) in the cylinder block 13 of the engine 10. A check valve 48 is supported in the passage 46 to allow flow through the passage 41 from the lowermost area 39 in the first crankcase chamber 23 only when a reduced pressure exists in the cylinder 15 with which the passage 46 communicates.

When the check valve 48 opens, drainage flows from the lowermost area 39 through the passages 41 and 46 to a passage or duct 49 (see FIG. 3) in the cylinder block 13 of the engine 10. The transfer duct 49 communicates with a boost port 50 of the cylinder 15. The boost port 50 is preferably disposed between the two transfer ports 29 of the cylinder 15 as shown in FIG. 4.

The third crankcase chamber 25 also communicates with the passage 41 by means of a check valve 51 (see FIG. 2) and a passage 52 in the crankcase 11. Thus, drainage can flow from the third crankcase chamber 25 to the passage 41 only when drainage is flowing through the passage 41 because of the check valve 48 being open.

The lowermost area or pocket 40 of the second crankcase chamber 24 communicates with a passage 53. The passage 53 extends along the sealing surface 43 of the crankcase 11. The passage 53 then extends through a hole 54 in the crankcase 11 and then along a surface 55 of the crankcase 11. The surface 55 cooperates with the end portion 32 of the reed block 22.

The passage 53 then extends along the sealing surface 45 of the crankcase 11 for communication with a passage 56 (schematically shown in FIG. 2) in the cylinder block 13 of the engine 10. The passage 56, which is formed in the cylinder block 13 in the same manner as the passage 46, has a check valve 57 supported therein to allow flow of drainage from the lowermost area 40 in the second crankcase chamber 24 only when reduced pressure exists in the cylinder 14 with which the passage 56 communicates.

When the check valve 57 opens, the drainage flows via the passage 56 through a transfer duct 58 (see FIG. 4) in the cylinder block 13 to a boost port 59 of the cylinder 14. The boost port 59 is preferably disposed between the transfer ports 27 of the cylinder 14 as shown in FIG. 4.

Accordingly, during each cycle of operation, drainage is withdrawn from the first crankcase chamber 23 and the third crankcase chamber 25 when a reduced pressure exists in the second crankcase chamber 24 as the piston 17 rises (and the transfer ports are closed thereby) and, similarily, from the second crankcase chamber 24 when a reduced pressure exists in the first crankcase chamber 23 as the piston 16 rises. Thus, drainage does not accummulate in any of the crankcase chambers 23-25 of the crankcase 11.

Additionally, the mixture of gasoline and oil can be supplied from a fuel tank 60 (see FIG. 3) to the boost port 59 of the cylinder 14 and the boost port 50 of the cylinder 15 when it is desired to prime the engine for starting.

The mixture of oil and gasoline is supplied from the fuel tank 60 through conduits 61 and 62 (see FIGS. 2 and 3) to the passages 46 and 56 in the cylinder block 13 whenever a primer control (shown schematically in FIG. 3) is opened by the operator depressing a button. The depressing of the primer button opens the primer check valve and supplies the mixture of oil and gasoline to the passages 46 and 56 from where it is sucked into the cylinders through the transfer passages 49 and 58 by cranking or operation of the engine.

Accordingly, the present invention allows the mixture of gasoline and oil to be supplied from the fuel tank 60 to both of the cylinders 14 and 15 for priming purposes. Furthermore, there is no collection of any drainage in any of the chambers 23-25 of the crankcase 11.

An advantage of this invention is that it smooths out the idle and acceleration characteristics of the engine since there is no fouling of the plugs due to puddling. Another advantage of this invention is that it reduces the smoky exhaust. A further advantage of this invention is that there is more complete burning of the mixture of oil and gasoline. Still another advantage of this invention is that it drains the drainage from all chambers of the crankcase. A still further advantage of this invention is that the fuel mixture can be enriched without directing the enriching oil and gasoline mixture through the carburetor.

For purposes of exemplification, a particular embodiment of the invention has been shown and described according to the best present understanding thereof. However, it will be apparent that changes and modifications in the arrangement and construction of the parts thereof may be resorted to without departing from the spirit and scope of the invention.

What is claimed is:

1. In a two-cycle internal combustion engine including a cylinder head, two cylinders and transfer ducts therefor, a crank case, a reed block, and means for providing a fuel-oil-air mixture to said cylinders through said reed block and transfer ducts, wherein said reed block divides said crank case into two compression chambers and a reed block chamber, improved means for recirculating crank case residuals comprising, a passage connecting each compression chamber to a transfer duct of the other cylinder, a passage connecting the reed block chamber to one of said passages, and means in said passages for preventing flow other than toward said transfer ducts, whereby flow through said one passage includes residuals from only one of said compression chambers and said reed block chamber.

2. The device of claim 1 further including means for providing priming fuel to the transfer duct of at least one of said cylinders.

3. The device of claim 1 wherein said cylinder head and crank case join along a common surface and wherein a portion of each of said passages joining said compression chambers to said transfer ducts communicate with said surface.

4. The device of claim 3 wherein said reed block and said crank case meet along a common surface and wherein a portion of said passages connecting said compression chambers to said transfer ducts communicate with said common surface, whereby said passages are substantially exposed by disassembly of said cylinder head, crank case and reed block. 

1. In a two-cycle internal combustion engine including a cylinder head, two cylinders and transfer ducts therefor, a crank case, a reed block, and means for providing a fuel-oil-air mixture to said cylinders through said reed block and transfer ducts, wherein said reed block divides said crank case into two compression chambers and a reed block chamber, improved means for recirculating crank case residuals comprising, a passage connecting each compression chamber to a transfer duct of the other cylinder, a passage connecting the reed block chamber to one of said passages, and means in said passages for preventing flow other than toward said transfer ducts, whereby flow through said one passage includes residuals from only one of said compression chambers and said reed block chamber.
 2. The device of claim 1 further including means for providing priming fuel to the transfer duct of at least one of said cylinders.
 3. The device of claim 1 wherein said cylinder head and crank case join along a common surface and wherein a portion of each of said passages joining said compression chambers to said transfer ducts communicate with said surface.
 4. The device of claim 3 wherein said reed block and said crank case meet along a common surface and wherein a portion of said passages connecting said compression chambers to said transfer ducts communicate with said common surface, whereby said passages are substantially exposed by disassembly of said cylinder head, crank case and reed block. 